Stenotic and regurgitant unicuspid acommissural aortic valves in adults without mitral valve disease are likely congenital rather than acquired.
Five adults, aged 30-75 years, are described with stenotic and regurgitant unicuspid acommissural aortic valves. Because none of these patients had clinical, echocardiographic or hemodynamic evidence of mitral valve disease, a case is made that these valves were congenitally malformed and not the result of an acquired condition.
Roberts et al. (2006) studied this question.